The present invention relates to an apparatus for reducing the pressure of a piston exerted on a cylindrical inside wall of a cylinder of a reciprocating internal combustion engine.
Japanese patent Laid-Open Application No. 56-98531 has disclosed an apparatus in which the axis of a crankshaft is offset from the axis of a cylinder for reducing the pressure of a side of a piston against the inside wall of the cylinder. Explosion pressure exerted on the top of the piston is divided into an axial component and a radial component. The radial component of the explosin pressure acts to push the piston against the inside wall of the cylinder, so that friction between the piston and the cylinder wall increases, resulting in a decrease of the output of the engine. In this prior art, the offset distance is calculated from experimentally to be more than 10% and less than 45% of the piston stroke. However, the problem is that the explosion pressure is not effectively converted to the rotation of the crank shaft because the crank and the connecting rod are aligned with each other at the top dead center.